This copy is for your personal non-commercial use only. To order presentation-ready copies of Toronto Star content for distribution to colleagues, clients or customers, or inquire about permissions/licensing, please go to: www.TorontoStarReprints.com

A “superbug” strain of the bacterium that causes typhoid fever has spread globally in just three decades and is currently seeding a silent epidemic in Africa, according to a, international study.

In the aftermath of the recent earthquake in Nepal, a mother in Kathmandu cares for her 3-year-old daughter, who is suffering from typhoid fever. New research has found a "superbug" strain of the disease is spreading globally, hitting Africa especially hard. (David Ramos / GETTY IMAGES file photo)

A “superbug” strain of the bacterium that causes typhoid fever has spread globally in just three decades and is currently seeding a silent epidemic in Africa, according to a study in the journal Nature Genetics.

An international team of researchers on Monday reported that typhoid fever — a centuries-old disease that still afflicts millions of people in the developing world — has been quietly shape-shifting into a deadlier threat, thanks to the rapid emergence of a drug-resistant strain called H58.

The strain refers to a family of Salmonella enterica Typhi (the bacterium that causes typhoid fever) that has developed resistance to antibiotics commonly used to treat the disease. In recent years, public health officials have seen H58 popping up in countries like Vietnam and Malawi but this latest study is the first to provide a snapshot of the superbug’s global spread.

In a major international collaboration, more than 70 researchers analyzed 1,832 samples of S. Typhi collected from 63 countries. Twenty-one of those countries had H58, which has “expanded dramatically” across Asia and Africa since first emerging three decades ago, the study found. The superbug is also now moving across Africa, where it is causing an “ongoing, unrecognized multi-drug resistant epidemic.”

“One of the surprising findings was that when we sequenced all these . . . almost half of them fell into the H58 lineage,” said first author vkw23@cam.ac.uk ">Dr. Vanessa Wong, an infectious disease specialist with the Wellcome Trust Sanger Institute and University of Cambridge.

Article Continued Below

“That (covered) 21 countries. So we were like, oh no. This is actually kind of everywhere.”

Typhoid fever is a disease that can be spread by only humans who carry the S. Typhi bacterium in their bloodstreams and intestinal tracts.

The disease is now rare in industrialized countries like Canada — which had 144 reported cases in 2012, probably mostly in travellers — but it is still relatively common in the developing world, especially where hygiene and sanitation are poor.

While a typhoid vaccine is available, its efficacy wears off after a few years and many people also can’t afford the vaccine in the developing world, where the disease is estimated to cause 21 million cases every year and about 200,000 deaths.

Typhoid fever can be treated with antibiotics but the overuse of these drugs has fuelled resistance, as bacteria capable of defeating these drugs survive and proliferate. In a 2013 report, the Public Health Agency of Canada found that S. Typhi infections resistant to the antibiotic ciprofloxacin had increased to 18 per cent from 10 per cent the previous year.

When asked if H58 has ever been reported in Canada, the agency said it doesn’t routinely analyze the strains of S. Typhi cases since typhoid fever is not endemic here.

In countries where H58 has emerged, the superbug is now crowding out weaker strains, thus dramatically “changing the architecture of the disease,” Wong said.

She said treating multidrug-resistant strains like H58 also requires intravenous antibiotics — an expensive luxury that many people in the developing world cannot access or afford. Resistance against last-line antibiotics will probably also eventually emerge, she added. “If we carry on and the bug continues to evolve, we’ll run out of options pretty quickly.”

She noted that her study also found H58 in Nepal, where devastating earthquakes have now left the country highly vulnerable to outbreaks of diseases like typhoid fever.

For Virginia Pitzer, a professor of epidemiology with the Yale School of Public Health who was not involved with this study, this “important and interesting” new paper underscores the need to tackle typhoid fever, a disease that has long been neglected by the global community.

“It’s going to be a problem for years to come and some of the traditional ways of treating typhoid are not going to be as effective anymore,” Pitzer said. “We’re going to have to come up with better ways to control the disease.”

More from the Toronto Star & Partners

LOADING

Copyright owned or licensed by Toronto Star Newspapers Limited. All rights reserved. Republication or distribution of this content is expressly prohibited without the prior written consent of Toronto Star Newspapers Limited and/or its licensors. To order copies of Toronto Star articles, please go to: www.TorontoStarReprints.com